Electric switch structure having externally accessible drift-free adjustment



Dec. 26, 1967 L. ERWIN ETAL ELECTRIC SWITCH STRUCTURE HAVING EXTERNALL3,360,624 Y ACCESSIBLE DRIFTFREE ADJUSTMENT Filed Oct. 25, 1965 Z L j"'llz 32 26 INVENTORS CAF/L L [QW/N @5050/125 G JWM/@ m' M 'd-d TTORNEYSUnited States Patent O 3,360,624 ELECTRIC SWITCH STRUCTURE HAVINGEXTERNALLY ACCESSIBLE DRIFT-FREE ADJUSTMENT Carl L. Erwin and TheodoreG. Scheid III, Chicago, Ill., assignors to Northern Electric Company,Chicago, Ill., a corporation of Delaware Filed Oct. 23, 1965, Ser. No.503,954 Claims. (Cl. 200--138) ABSTRACT 0F THE DISCLOSURE An electricalswitch structure includes a metal case having a tubular deformation-freeportion which receives contact blades, the xed ends of the blades beingrigidly supported by a rigid insulator and separated from each other byan insulative slida'ble member that holds the parts together `and alsohas a cam portion that coacts with a dimple on one blade for adjustingthe contact of one blade away from that of the other.

This invention relates generally to electric switches, and morespecifically to a switch structure which embodies a slidably movableinsulative spacer disposed between elements thereof.

Although the principles of the present invention may be includes invarious switches, a particularly useful application is made in aminiaturized switch, particularly where such switch is a thermostaticlimit switch.

In the assembly and calibration of miniaturized thermostatic switches,some form of calibration is necessary. Prior switch structures havenecessitated permanent bending of a blade, bending of a metallic case,bending of a tongue which is integral with a 4metallic case, or formingan indentation in a metallic case. In all such instances, a calibrationforce is applied to the part to be permanently deformed, whichinherently has a degree of resiliency so that such part being bentsprings back to some extent. This factor makes calibration techniquesand apparatus quite cumbersome since the part must be deflected beyondthe point where it should remain when properly calibrated.

The present invention is particularly useful in connection with such aminiaturized thermostat and includes a slidably movable wedge whichholds the components together equally well at all positions, and whichfurther, depending on its position, effects proper calibration of thedevice. In such structure, there is no permanent deformation of anyresilient element as a part of the calibration process, and thereforecalibration is achieved by positive displacement as there is nospring-back involved.

Accordingly, it is an object of the present invention to provide a novelswitch construction.

A further object of the present invention is to provide a switchconstruction wherein the spring-back problem is entirely eliminated fromits calibration process.

Yet another object of the present invention is to provide a switchconstruction which is particularly adapted to be manufactured inminiaturized form.

A still further object of the present invention is to provide aheavy-duty industrial type of switch is a minimum amount of volumetricspace.

Many other advantages, features and additional objects of the presentinvention will become manifest to those versed in the art upon makingreference to the detailed description and to the accompanying sheet ofdrawings in which a preferred structural embodiment incorporating theprinciples of the present invention is shown by way of illustrativeexample.

ICC

On the drawings:

FIG. l is a side elevational View, drawn in actual size, of athermostatic switch provided in accordance with the principles of thepresent invention;

FIG. 2 is an enlarged cross-sectional view of the switch of FIG. l;

FIG. 3 is an enlarged end View of the switch of FIG. l;

FIG. 4 is a fragmentary cross-sectional view taken along line IV-lV ofFIG. 2;

FIG. 5 is a fragmentary cross-sectional view of the xed end of a bladeshown in its disassembled state; and

FIG. 6 is an enlarged cross-sectional view of a modified form of theswitch shown in FIG. 2.

As shown on the drawings:

The principles of this invention are particularly useful when embodiedin an electric switch such as illustrated `n FIG. 1, generally indicatedby the numeral 10. In actual size, this switch is approximately 0.80inch in length exclusive of the terminals, and as such is termed aminiaturized switch. As shown in FIG. 2, the switch 10 includes a rstelectric contact blade 11, a second electric contact blade 12, a bimetalblade 13, an insulative spacer 14, and rigid means generally indicatedvat 15 for holding the blades 11-13, such rigid means comprising aninsulative spacing member 16 and a tubular case 17.

The electric contact blade 11 has a movable end 18 to which there issecured an electric contact 19. Intermediate its ends, the contact blade11 has a projection or cam portion 2i). The contact blade 11 has a fixedend 21 best seen in FIG. 4 which includes a pair of oppositely directedshoulders 22, 23 which coact with a pair of oppositely directedshoulders 24, 25 on the insulative spacing member 16. The rigid end 21of the contact blade 11 further has an integral spring 26 whichcomprises a struck-out portion which normally projects from the plane ofthe fixed end 21 as shown in FIG. 5. However, in assembly, theassociated elements hold the struck-out portion or spring 26 in aposition which is substantially coplanar with such xed end 21.

The contact blade 12 is identical to the contact blade 11 forinterchangeability, which blades further include a second projection 27near the movable end 18 thereof.

The b imetal blade 13 has a thickness which is greatly exaggerated inFIG. 2 to facilitate illustration. At its tixed end, the bimetal blade13 has oppositely directed shoulders similar to the shoulders 22, 23described above which coact with the insulative spacing member 16 in themanner described. The bimetal blade 13 has an aperture 28 which receivesthe projection 20 of the blade 12. The movable or free end of thebimetal blade 13 engages the projection 27 of the contact blade 12. Thebimetal blade 13 has a high expansion side 29 which faces the contactblade 11, and in response to a predetermined temperature, the bimetal13, acting through the projection 27, causes the -contacts 19 of thecontact blades 12 and -11 to separate. If desired, the electric contactblade 12 and the bimetal blade 13 may be jointly reversed so that thehigh expansion side 29 is directed away from the contact blade 11. Withsuch construction, the contacts 19 are normally open, and move to aclosed position in response to a suitable temperature increase.

The insulative spacer 14 comprises plastic and has an inner end 30 whichserves as a cam or wedge and acts on the projection or cam portion 20 ofthe contact blade 11. The insulative spacer 14 is made symmetrical sothat either side will present such a cam surface 30.

The rigid means 15 extends about the fixed ends 21 of the contact blades11 and 12, extends Iabout the fixed end of the bimetal blade 13, as wellas about the rigid insulative spacer 14. To this end, the rigid means 15includes the insulative spacing member 16 which in this embodiment isprovided as a pair of spacing member sections 16a and 16b. The outer endof the spacing member 16 comprises a ange 31 against which the case 17abuts, while the inner end is beveled as at 32 to facilitate assembly.For the same purpose, the entrant end of the case 17 is likewisebeveled, and therefore the flange 31 has a complemental beveled surface.As seen in FIGS. 2 and 4, the insulative spacing member 16 holds thevarious blades 11- 13 in spaced relation to the conductive case 17, andtherefore the case 17 is electrically dead or neutral. The insulativespacing member also comprises plastic, but for higher temperatureapplications, the plastic components may be replaced with similarceramic components. The spacing member sections 16a and 16b are heldtogether by the entrant or open end of the tubular case 17, such caseend tightly encircling the spacing member 16.

Suitable conductors 33 may be soldered or otherwise secured to theexposed ends of the contact blades 11, 12.

The switch is assembled readily by hand and the insulative spacer 14 ispartially inserted. As soon as the cam portion 3@ thereof has fullyentered, the spacer 14 tightly urges the blades 11-13 against the rigidmeans 15 and holds the contact blades 11, 12 in spaced juxtaposition toeach other. Such assembly also serves to deflect the spring means 26into the plane of the contact blade 11 or 12, which spring means thusact perpendicularly to the direction of spacer movement, and augment thefrictional resistance to sliding ot such spacer 14. The shoulder means22-25 preclude movement of any of the blades 11-13 in either directionparallel to the direction of movement of the spacer 14.

After the spacer has entered 4to the degree necessary to engage the camportion 30 of the spacer with the cam portion 20 of the contact blade11, further movement serves to preset or adjust the relative position ofthe movable ends 18, which constitutes the calibration of thethermostatic switch 10. By this means of calibration, such presetting isaccomplished without permanently bending any element, and can beaccomplished by direct ydisplacement means. When such calibration hasbeen completed, it is preferable that the cavity yat the outer end ofthe insulative spacer 14 be covered with glyptol or the like the serveas a lock, and as an indicator as to possible subsequent tampering withits position. If desired, the joint between the cover 17 and the flange31 may be varnished or otherwise sealed, and likewise, the variousjoints shown in FIG. 3 may be sealed if desired.

When the contact blades 11 and 12 comprise Phosphor bronze, and when aseparate bimetal 13 is employed as shown in FIG. 2, the disclosedembodiment may be used for heavy duty industrial applications, eventhough the same is of miniaturized size. By heavy duty industrialapplications is meant that the switch will readily achieve a 7.5-ampererating under standards established by Underwriters Laboratories. Where alower electrical rating will suice, one contact blade 34 may comprise abimetal as shown in FIG. 6, such blade 34 having a lixed end withshoulder means as shown at 22, 23 in FIG. 4. The bimetal contact blade34 is illustrated in exaggerated thickness for clarity of illustration.However, a slightly thickened insulative spacing member section 16C maybe employed in place of the section 16a to compensate for the netdifference in thickness. The switch shown in FIG. 6 is otherwise thesame as that shown in FIG. 2.

Although various minor modifications might 'be suggested by those versedin the art, it should be understood that we wish to embody within thescope of the patent warranted hereon all such embodiments as reasonablyand properly come within the scope of our contribution to the art.

We claim as our invention:

1. An electrical switch structure, comprising in combination:

(a) a case of metal having a tubular configuration free of deformation;

(b) an electrical contact supported therein;

(c) an electrical contact blade having a fixed end and a movable contactend engageable with said contact;

(d) separate rigid insulative means fixedly disposed free of deformationwithin an end of said tubular case and tightly encircled by thedeformation-free tubular case, said rigid means extending about said xedend of said blade in spaced relation to one side thereof so as to leavea space therebetween within said rigid means, such space extending fromoutside of said case into the interior of said case;

(e) a separate insulative spacer disposed against said one side of saidblade and coacting with said rigid means in rigidly supporting saidfixed end, said spacer closing said space and being externallyaccessible for being slidably moved while coacting in the rigid supportof said fixed end; and

(f) spring means acting on said slidable spacer in a directionperpendicular to the direction in which said spacer is slidable, andaugmenting the frictional resistance of said spacer to sliding.

2. A switch structure according to claim 1, in which said spring meansis a struck-out portion of said lixed end of said blade, said portionbeing held against its resilience by said slidable spacer in a positionwhich is substantially coplanar with said fixed end.

3. In an electrical switch structure, the combination comprising:

(a) a pair of electrical contact blades arranged in spaced juxtapositionto each other, and each having lixed and movable ends, one of saidblades having a cam portion projecting as a dimple therefrom;

(b) rigid means extending about and supporting the fixed ends of saidblades remotely from said dimple, and insulating said fixed ends fromeach other; and

(c) an insulative spacer slidably movably disposed between said fixedends and yurging them against said rigid means, said spacer having a camportion projecting beyond said rigid means and being further engageablewith said dimple for moving one of said movable ends away from theother.

4. In an electrical switch structure, the combination comprising:

(a) a pair of electrical contact blades arranged in spaced juxtapositionto each other, and each having fixed and movable ends, one of saidblades having a cam portion projecting as a dimple therefrom;

(b) rigid means extending about and supporting the fixed ends of saidblades remotely from said dimple, and insulating said iixed ends fromeach other;

(c) an insulative spacer slidably movably disposed between said xed endsand urging them against said rigid means, said spacer having a camportion projecting beyond said rigid means and being further engageablewith said dimple for moving one of said movable ends away from theother; and

(d) a third blade, said third blade being of bimetal material, extendingalong and having its low expansion side disposed against the other ofsaid contact blades, and having a lixed end supported by said rigidmeans;

(e) said bimetal blade and said other contact blade being selectivelypositionable as a pair in one position with the high-expansion side ofthe bimetal blade directed toward said one contact blade to provide anormally closed switch, and in a second position with said highexpansionside of the bimetal blade directed away from said one contact blade toprovide a normally open switch.

5. An electrical switch structure, comprising in combination:

(a) a case of metal having a tubular configuration free of deformation;

6 (b) a pair of electrical contact blades disposed in said said rigidmeans and being further engageable with case and arranged in spacedjuxtaposition to each said dimple for moving one of said movable endsother, and each having fixed and movable ends, one away from the other.of said blades having a cam portion projecting as a dimple therefrom; 5References Cited (c) separate rigid insulative means xedly disposedUNITED STATES PATENTS free of deformation within an end of said tubularT case and tightly encircled by the deformation-free Re'24308 4/1957Colegrove' tubular case, said rigid means extending about saidlmelsbaugh zogofl fixed ends of said blades remotely from said dimplc 102717937 9/1955 L ly -t-- "2 00 E9 X and leaving a space between saidblades within said 2871315 1/1959 Delf e a 2E) 138 rigid means, SuchSpace extending from outside of 881,290 4/1959 Dales 20o-138 Said caseinto the interior of said case; and 2,944,324 7/1960 Ma es 60 g8 X (d)an insulative spacer slidably movably disposed be- 3066206 11/1962 DO15/ef tween said xed ends and urging them against Said 15 a es 20o- 13grigid means, said spacer closing said space and being l y externallyaccessible for being slidably moved while BERNARD A GILHEANY P'lma')Examme" coacting in the rigid support of said fixed ends, and H- A-LEWITTER, SSSHHI Examiner. said spacer having a cam portion projectingbeyond

1. AN ELECTRICAL SWITCH STRUCTURE, COMPRISING IN COMBINATION: (A) A CASEOF METAL HAVING A TUBULAR CONFIGURATION FREE OF DEFORMATION; (B) ANELECTRICAL CONTACT SUPPORTED THEREIN; (C) AN ELECTRICAL CONTACT BLADEHAVING A FIXED END AND A MOVABLE CONTACT END ENGAGEABLE WITH SAIDCONTACT; (D) SEPARATE RIGID INSULATIVE MEANS FIXEDLY DISPOSED FREE OFDEFORMATION WITHIN AN END OF SAID TUBULAR CASE AND TIGHTLY ENCIRCLED BYTHE DEFORMATION-FREE TUBULAR CASE, SAID RIGID MEANS EXTENDING ABOUT SAIDFIXED END OF SAID BLADE IN SPACED RELATION TO ONE SIDE THEREOF SO AS TOLEAVE A SPACE THEREBETWEEN WITHIN SAID RIGID MEANS, SUCH SPACE EXTENDINGFROM OUTSIDE OF SAID CASE INTO THE INTERIOR OF SAID CASE; (E) A SEPARATEINSULATIVE SPACER DISPOSED AGAINST SAID ONE SIDE OF SAID BLADE ANDCOACTING WITH SAID RIGID MEANS IN RIGIDLY SUPPORTING SAID FIXED END,SAID SPACER CLOSING SAID SPACE AND BEING EXTERNALLY ACCESSIBLE FOR BEINGSLIDABLY MOVED WHILE COACTING IN THE RIGID SUPPORT OF SAID FIXED END;AND (F) SPRING MEANS ACTING ON SAID SLIDABLE SPACER IN A DIRECTIONPERPENDICULAR TO THE DIRECTION IN WHICH SAID SPACER IS SLIDABLE, ANDAUGMENTING THE FRICTIONAL RESISTANCE OF SAID SPACER TO SLIDING.